The Black Death was a very bad sickness that happened a long time ago. It killed a lot of people in Asia and Europe. It spread from one place to another through trade routes. It happened many times over a few hundred years. It spread quickly from person to person and usually caused death in three days. People didn’t know what caused the disease or how to cure or stop it. But in the 17th century, they started making people stay inside their houses for 40 days if someone in their house had the disease.

Smallpox was another bad disease that spread in many parts of the world from the 6th to the 18th centuries because of trade and exploration.

In 1796, a doctor named Edward Jenner noticed that girls who took care of cows got a disease called cowpox, which was like smallpox, but they didn’t get smallpox. He gave a boy cowpox and then later gave him smallpox. The boy didn’t get sick. Jenner called this process “vaccination” and by 1853, everyone in Britain had to get vaccinated against smallpox. In 1980, the World Health Organization said that smallpox was gone.

In the 19th century, there were other serious health problems like cholera, tuberculosis, and typhoid. Cholera made a lot of people sick and killed many people. They found out that it was caused by dirty water. When they started giving people clean water and sewers, fewer people got sick.

In the 20th century, diseases like the flu and tuberculosis were common. The flu pandemic in 1918 killed a lot of people. But they made vaccines for the flu in the 1930s and found medicine to treat tuberculosis in the 1950s.

In the 21st century, most people get vaccines when they are young to protect against diseases like measles, rubella, diphtheria, tetanus, and polio. But new diseases like SARS, MERS, and COVID-19 are still a problem for doctors.